Inkjet printers print dots by ejecting very small drops of ink onto a print substrate. In inkjet printers, the print substrate is traversed beneath one or more print cartridges, each having a printhead with a nozzle array. The nozzle array has an array length along the direction of substrate transition. Ink ejecting nozzles may be disposed along this length.
An ink supply, such as an ink reservoir, supplies ink to the nozzles. The nozzles are controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller. The timing of the application of the ink drops is intended to correspond to the pattern of pixels of the image being printed. In some inkjet printers, the print cartridges are mounted on a movable carriage. During printing, the carriage traverses over the surface of the print substrate for printing a portion of the image equivalent to a printhead swath. In some other inkjet printers, the printhead is a page wide array printhead that spans the whole portion of the substrate to be printed. During printing, nozzles in a page wide array printhead are selectively fired to reproduce the image on the substrate.
Inkjet printers may be operated using a multi-pass print mode (also referred to as shingling). In multi-pass print mode for printers with scanning printheads, the media only advances a fraction of the total length of a nozzle array after each printing pass of the printhead. In multi-pass print mode for printers with page wide array printheads, the media only advances a fraction of the total length of a nozzle array after the nozzles in the printhead are selectively fired. In a multi-pass print mode, each strip of the image to be printed is formed in successive passes of the printheads. Multi-pass print modes facilitate enhancing quality of a printed image. For example, multi-pass print modes facilitate decreasing the ink amount to be applied on a substrate region at a single time, thereby promoting ink absorption by the substrate. Further, multi-pass print modes are, generally, more robust to defects and non-uniformities in nozzles.
A print mode may have a number of parameters such as the number of passes required to fill an area, and the position of the ink droplets at every pass. To define such features, a print mask may be created that defines each position of each pass in which a drop may print. A print mask refers to logic that includes control data determining which nozzles of the different printheads are fired at a given time to eject fluid in order to reproduce a specific printjob. A print mask for an inkjet printer in multi-pass print mode is also referred to as shingling mask.